This application claims priority of Italian Patent Application No. 01830676.1 filed Oct. 30, 2001, and invented by Silvano Prampolini.
Specifically, though not exclusively, the invention can be used for enmeshing gears used, for example, in power take-offs applied in vehicle transmissions. In particular, the linear actuator of the invention, when applied to a gear clutch, must be able to control a precisely-staged sequential engagement operation, wherein an axially-mobile gear is brought into contact with an axially-fixed gear wheel and is kept pressed against the latter until, by effect of a relative rotation, the gears of one wheel coincide with those of the other and enmeshing takes place. The actuator of the invention must also include an endrun stage, in which the enmeshing is completed, and a return run for de-clutching.
Many and various prior art solutions are proposed for linear actuators, able to carry out the following functions: for example, EP 0 936 380 describes an actuator which solves a series of problems and drawbacks in prior art actuators. However these prior art solutions, including EP 0 936 380, can be improved in various ways.
Firstly, improvements can be made in constructional simplicity and reduction of mass.
Secondly ease of manoeuvre for the operator can be improved.
Thirdly, functional reliability is open to improvement.
The main aim of the present invention is to obviate the above limitations and drawbacks of the prior art.
An advantage of the invention is that it provides an actuator which is constructionally simple and of small mass.
A further advantage consists in the ease and immediacy with which the actuator can be manoeuvred and controlled.
A further advantage is the reliability of the actuator of the invention.
These aims and advantages and others besides are all attained by the present invention, as it is characterised in the appended claims.